In recent years, a light emitted diode (LED) with low power consumption and long life has been attracting attention, and an illumination device which has an LED as a light source has often been used instead of an illumination device in related art that has an incandescent light bulb as a light source. In the illumination device that has an LED as the light source, an illumination device has been suggested which is capable of dimming for changing beams and of toning for changing emission colors (for example, see PTLs 1 to 4 and so forth).
In an illumination device of PTL 1, current is supplied from a power source unit to plural light sources (white light and incandescent-lamp color light) with different emission colors, in the power source unit, two step-down chopper circuits are connected in parallel with an output end of a boost chopper circuit, and an LED unit of white light and an LED unit of incandescent-lamp color light are respectively connected with the step-down choppers. In addition, a current is independently supplied to each of the LED unit of the white color light and the LED unit of the incandescent-lamp color light, and dimming and toning are thereby performed.
A light emitting device in PTL 2 includes a first LED and a second LED that have different emission colors and are connected in parallel with each other, and a resistance which is in series connected with the first LED is provided. In addition, the voltage is changed by using differences in the change characteristic between a forward current of the first LED and the forward current of the second LED in a case where a power source voltage is changed, the ratio between a beam emitted from the first LED and a beam emitted from the second LED in all the beams is thereby changed, and dimming and toning are simultaneously performed.
An illumination device of PTL 3 includes a first light emitting unit and a second light emitting unit with different emission colors and includes a switching element that is disposed in series with the second light emitting unit on a second current path through which current flows to the second light emitting unit. In addition, ON and OFF of the switching element are switched in accordance with a signal from a selection control circuit, and to which of the first light emitting unit and the second light emitting unit the current flows is thereby selected. Accordingly, toning is performed.
An LED illumination device of PTL 4 includes plural LED groups in which plural LEDs are directly connected together in a forward direction. The plural LED groups have different total forward voltages, which are the totals of forward voltages of the plural LEDs. In the LED groups other than the LED group that has the maximum total forward voltage, a switching element connected in series is connected in series with the plural LEDs. In addition, the switching element is turned ON or OFF by a control signal from a control unit, and the current is thereby selectively caused to flow through any of the plural LED groups. Accordingly, dimming or toning is performed.